Infection Rates in Open Fractures of the Tibia: Is the 6-Hour Rule Fact or Fiction?

Aims. Emergency debridement has long been the standard of care for open fractures of the tibia as infection is an important complication. The timing of operative debridement can be debated. We review open fractures of the tibia and compare infection rates in those that were operated on within and after 6-hours. Method. 103 consecutive open fractures of the tibia were reviewed. The data was analysed retrospectively with regard to severity of fracture and incidence of infection. Infection rates over a three-month period were compared between the two groups. Results. 12 (11.6%) patients developed an infection within the first 3 months of injury. 7 of which were taken to theatre within 6-hours, and 5 after 6-hours. No significant differences were found between these two groups. Conclusion. There is no significant difference in timing of surgery. Initial basic interventions may play more of a role in limiting the risk of infection

Fifth International Conference on SALT WEATHERING OF BUILDINGS AND STONE SCULPTURES:

These proceedings report on the 5th edition of the conference, after Copenhagen (2008), Cyprus (2011), Brussel (2014) and Potsdam (2017), and it is the first time the conference is held in hybrid form, due to the COVID-19 pandemic. It is a challenge to organize an event in such an uncertain situation and to make it as attractive and interactive as the previous editions. We hope to meet your expectations! I’m very glad, that despite the situation, the interest for the conference is strong: we have received more than 40 contributions from 18 countries from all over the world. This confirms the relevance of the problem of salt weathering for the built cultural heritage and stone artifacts in a wide range of environments. Moreover, the broad spectrum of approaches to the subject presented in these proceedings highlights the importance of the interaction between different disciplines as well as between fundamental research and practice of conservation. I wish this conference to contribute to this fruitful exchange, and to generate new research ideas, whilst strengthening and broadening interdisciplinary collaborations. On behalf of the organizing committee, I’m looking forward to welcoming as many as possible of you in Delft. We hope that, next to participation to the conference, you will find some free time to visit the city. You can stroll along the canals, enter a windmill, visit the Prinsenhof museum and the Blue Delft Factory, admire the architecture and sculptures in the Old and New Church and, if you are looking for a real Dutch experience, you can rent a bicycle and visit the surroundings! This event would not have been possible without the collaboration of several persons. I would like to thank, on behalf of us all, the Scientific Committee for carefully reviewing the papers and contributing thereby to the high quality of the published contributions. My personal thank goes to the organizing committee who significantly contributed to the organization of this event and to the preparation of the proceedings. Last but not least, I’d like to thank the Cultural Heritage Agency of the Netherlands for co-sponsoring the event and RILEM (International Union of Laboratories and Experts in Construction Materials, Systems and Structures) for contributing to the dissemination

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Aims. Emergency debridement has long been the standard of care for open fractures of the tibia as infection is an important complication. The timing of operative debridement can be debated. We review open fractures of the tibia and compare infection rates in those that were operated on within and after 6-hours. Method. 103 consecutive open fractures of the tibia were reviewed. The data was analysed retrospectively with regard to severity of fracture and incidence of infection. Infection rates over a threemonth period were compared between the two groups. Results. 12 (11.6%) patients developed an infection within the first 3 months of injury. 7 of which were taken to theatre within 6-hours, and 5 after 6-hours. No significant differences were found between these two groups. Conclusion. There is no significant difference in timing of surgery. Initial basic interventions may play more of a role in limiting the risk of infection

Alkali silica reaction in the afsluitdijk: Assessment of concrete damage and remaining service life using experimental and modelling research

Alkali Silica Reaction (ASR) is one of the degradation mechanisms in concrete that poses a threat to the service life of existing structures. This physio-chemical process is progressive and can affect the the strength, stiffness and stability of concrete structures. A lot of mitigation measures are available to prevent the deleterious effects of ASR in new structures. However, assessment and monitoring of ASR in the existing structures still remain a challenge. Thus the main aim of this thesis is to develop a simplified tool for the assessment of existing structures to assist the asset owners in decision making. This is addressed by a combination of petrographic techniques to quantify the damageand development of a numerical model to predict the remaining service life. Various existing petrographic tools (Damage rating index and image analysis) are investigated and modified to not only identify the ASR signs but also to quantify the damage. A meso-scale numerical model (ASR expansion model) is developed as an extension to the existing Delft Lattice Model to incorporate the effect of ASR by application of randomly distributed internal expansions. A case study (Afsuitdijk, The Netherlands) is used to apply these methods. The model is compared with the findings from the petrographic analysis using a physical parameter 'crack densities'. This model is able to simulate localised network of cracks typical of ASR and expansion strains as a function of time. These expansions are compared with the permissible expansion thresholds set byRILEM and CUR to assess the remaining service life. Additionally, the numerical model showcases the importance of different boundary conditions by making a comparative study between free expansions and concrete in confined state. Finally, the limitations and drawbacks of this expansion model are discussed critically.Civil Engineering | Structural Engineering | Concrete Structure

Leaching behaviour of a crystallisation inhibitor in mortars

This paper investigates the leaching behaviour of sodium ferrocyanide, a known crystallisation inhibitor of sodium chloride, which is added to mortars for mitigation of salt decay. Leaching and depletion of the inhibitor is a practical performance related issue that might over time, make the inhibitor less effective against salt decay. In this research, the inhibitor was added to natural hydraulic lime (NHL) mortars during the mixing stage. Leaching of the inhibitor from the hardened mortar was assessed experimentally in laboratory. Both diffusion- and advection-driven transport mechanisms were considered. Diffusion experiments were carried out in a tank leaching test setup. Capillary absorption and drying cycles were used as a driving force to study advection-driven transport. Quantification of the leached species was carried out using various analytical techniques, including UV-VIS spectroscopy, ICP-OES and ion chromatography. The results from the tank leaching test show a high effective diffusion coefficient of ferrocyanide ions, in the same order of magnitude as sodium chloride transport. The advection test shows accumulation of the inhibitor at the evaporative surface and depletion of the inhibitor in the inner layers with successive wet-dry cycles. Based on these results it can be inferred that the degree of inhibitor leaching is significant and needs to be minimised to prolong the positive effect of the inhibitor on mortar durability. Potential solutions to reduce inhibitor leaching are discussed.Heritage & ArchitectureMaterials and Environmen

Tunable chitosan-alginate capsules for a controlled release of crystallisation inhibitors in mortars

Plasters and renders used in historic monuments are vulnerable to degradation caused by salt weathering. Crystallisation inhibitors (molecules/ions that alter salt crystallisation) mixed into mortars have shown promising results in mitigating salt damage by inhibiting salt crystallisation, promoting salt transport to the evaporating surface, and modifying crystal habit. However, past research suggests that inhibitors easily leach out from mortars, meaning their long-term positive effect is lost. Encapsulation of an inhibitor within a mortar is a potential solution to minimise leaching. Herein, capsules composed of a polyelectrolyte complex of calcium alginate coated in chitosan are investigated for the controlled diffusive release of sodium ferrocyanide, a known NaCl crystallisation inhibitor. Capsules with varying chitosan-calcium alginate ratios are prepared using the extrusion dripping technique. The release of the inhibitor from capsules in solutions of various pH values ranging from 7–13 is investigated. Results show that increasing the capsule’s chitosan to calcium alginate ratio reduces the inhibitor release for all studied solution pH values compared to pure calcium-alginate capsules. Therefore, a controlled inhibitor release can be obtained by tuning the chitosan-alginate ratio. In future, additional tests will be performed to find suitable capsule compositions for optimising their performance when mixed in mortars.Heritage & ArchitectureMaterials and Environmen

Plasters with mixed-in crystallization inhibitors: Results of a 4-year monitoring of on-site application

Salt crystallization is a major cause of weathering of mortars, including plasters and renders. In the last decade, the use of mixed-in salt crystallization inhibitors in mortars has been proposed as a solution to improve the durability of this material with respect to salt decay. Laboratory characterization and accelerated weathering tests have shown encouraging results. However, data on the long-term behaviour of these mortars when applied on-site were missing until now .In this research the durability with respect to salt decay of a lime-based plaster and a salt accumulating plaster has been assessed. These plasters, with and without sodium ferrocyanide, a well-known inhibitor of sodium chloride crystallization, have been applied to an interior brick masonry wall with a high salt (sodium chloride) and moisture load and monitored for a period of 4 years. Monitoring included visual and photographic observations of the damage as well as measurements of the moisture and salt content and distribution, both in the wall and in the plaster. Moreover, the content and distribution of the inhibitor in the plaster after 4 year exposure was measured, to gain insight into the dissolution and transport of the inhibitor. The results of the research clearly show that the inhibitor is able to significantly reduce the occurrence of salt-induced decay in the lime-based plaster, in comparison to the plaster without inhibitor. No conclusions can be drawn in the case of the salt accumulating plaster, as no decay has developed yet in this case. Two issues related to leaching of the inhibitor and surface discolouration have emerged. These are discussed and possible solutions are proposed.Heritage & Technolog

Real-time chloride diffusion coefficient in concrete using embedded resistivity sensors

Service life of concrete infrastructure is severely compromised because of chloride-induced corrosion and measuring the chloride content is crucial to determine the remaining service life. DuraCrete provides a chloride ingress model based on Fick’s 2nd law. Although the diffusion coefficient is modelled as a time-dependent variable, the DuraCrete solution averages it to a constant value. This simplification leads to inaccurate estimation of the chloride content. A new analytical solution that addresses the underlying mathematical discrepancy has been proposed. However, the time-dependent diffusion coefficient is still based on an empirical factor. In this study, a real-time durability monitoring system has been developed using remotely operated resistivity sensors. Such a system is able to monitor the time dependent diffusion coefficient without the need to incorporate empirical factors. Additionally, a numerical technique to find an approximation of the proposed improved analytical solution is presented using real-time resistivity measurements from laboratory and real structures. The results show that the discrete sensor data measurements over time provide a good approximation of the proposed analytical solution. The system developed in this study is used as a data-driven input parameter to supplement the existing chloride models.Concrete Structure

Tunable chitosan-alginate capsules for a controlled release of crystallisation inhibitors in mortars

Plasters and renders used in historic monuments are vulnerable to degradation caused by salt weathering. Crystallisation inhibitors (molecules/ions that alter salt crystallisation) mixed into mortars have shown promising results in mitigating salt damage by inhibiting salt crystallisation, promoting salt transport to the evaporating surface, and modifying crystal habit. However, past research suggests that inhibitors easily leach out from mortars, meaning their long-term positive effect is lost. Encapsulation of an inhibitor within a mortar is a potential solution to minimise leaching. Herein, capsules composed of a polyelectrolyte complex of calcium alginate coated in chitosan are investigated for the controlled diffusive release of sodium ferrocyanide, a known NaCl crystallisation inhibitor. Capsules with varying chitosan-calcium alginate ratios are prepared using the extrusion dripping technique. The release of the inhibitor from capsules in solutions of various pH values ranging from 7–13 is investigated. Results show that increasing the capsule’s chitosan to calcium alginate ratio reduces the inhibitor release for all studied solution pH values compared to pure calcium-alginate capsules. Therefore, a controlled inhibitor release can be obtained by tuning the chitosan-alginate ratio. In future, additional tests will be performed to find suitable capsule compositions for optimising their performance when mixed in mortars